This is a safety and tolerance study of Lobucavir (BMS 180, 194). Study data show at dose levels of 20, 70, 200, or 400 mg twice daily for 28 days, this drug to be well tolerated with no adverse events attributable to the active drug. Pharmacokinetic data confirm this compound to be well absorbed orally. Recently, the protocol has undergone a revision to include the enrollment of individuals with advanced HIV infection (CD4 lymphocyte count < or = 200) who are taking the antiretroviral agent AZT and other concomitant medications. Another change is the recruitment of male AIDS patients with CMV positive semen and urine samples for analysis of potential antiviral effects. Higher dose levels of Lobucavir (BMS-180, 194) have been included for pharmacokinetic safety, tolerance, and antiviral analysis. These dose levels are 200 mg QID, 400 mg QID, and 800 mg QID.